"Charges were not likely to be filed, because Parker did not appear to know what had happened, where he was nor the correct date"
Yet, he was perfectly able to get into his car, start the ignition, put the car into "drive" but has no idea what happened. Hmmmmmmmmmmmmmm...............
I don't see why this is so hard to believe. For some people, cognitive decline might mean they lose their short-term memory while keeping all their long term memory.
They still remember everything they've learned in the past, before they lost their short-term memory, but new memories are impossible.
They can't tell you what happened even 5 minutes ago.
Having worked Alzheimer's patients, I can believe it. Both that he would get in the car, and that he would not remember the accident.